title: Isolated septal substrate for ventricular tachycardia in nonischemic dilated cardiomyopathy: incidence, characterization, and implications.
abstract: BACKGROUND
  The substrate for ventricular tachycardia (VT) in nonischemic cardiomyopathy (NICM) has a predilection for the basolateral left ventricle with right bundle branch block VT morphology.
  
  
  OBJECTIVE
  The purpose of this study was to describe a unique group of NICM patients with septal VT substrate.
  
  
  METHODS
  Between 1999 and 2010, 31 (11.6%) of 266 patients with NICM undergoing VT ablation had septal substrate and no lateral involvement. Mean age was 59 ± 12 years, and ejection fraction was 30% ± 14%. Eight patients had heart block.
  
  
  RESULTS
  Cardiac magnetic resonance showed septal delayed enhancement in 8 of 9 patients. Electroanatomic mapping demonstrated bipolar low voltage (<1.5 mV) extending from the basal septum in 22 of 31 patients. The remaining 9 patients had normal endocardial bipolar voltage but abnormal unipolar septal voltage (<8.3 mV) consistent with intramural abnormalities. Epicardial mapping in 14 patients showed no scar in 9 and patchy basal left ventricular summit scar in 5. VTs were mapped to the septal substrate, with 62% having right bundle branch block morphology and V(2) precordial transition pattern break in 17% suggesting periseptal exit. After substrate and targeted VT ablation, no VT was inducible in 66% and no "clinical targeted" VT in 86%. Over a mean follow-up of 20 ± 28 months, VT recurred in 10 (32%) patients.
  
  
  CONCLUSIONS
  Isolated septal VT substrate is uncommon in NICM. Biventricular low-voltage zones extending from the basal septum are characteristic, but septal scarring can be entirely intramural as evidenced by unipolar/bipolar electrograms and imaging. Multiple unmappable morphologies are the rule, often requiring several procedures aggressively targeting the septal substrate to achieve moderate long-term VT control.
authors.affiliation: Section of Cardiac Electrophysiology, Cardiovascular Division, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Haris M
authors.initials: HM
authors.lastname: Haqqani
authors.forename: Cory M
authors.initials: CM
authors.lastname: Tschabrunn
authors.forename: Wendy S
authors.initials: WS
authors.lastname: Tzou
authors.forename: Sanjay
authors.initials: S
authors.lastname: Dixit
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Cooper
authors.forename: Michael P
authors.initials: MP
authors.lastname: Riley
authors.forename: David
authors.initials: D
authors.lastname: Lin
authors.forename: Mathew D
authors.initials: MD
authors.lastname: Hutchinson
authors.forename: Fermin C
authors.initials: FC
authors.lastname: Garcia
authors.forename: Rupa
authors.initials: R
authors.lastname: Bala
authors.forename: Ralph J
authors.initials: RJ
authors.lastname: Verdino
authors.forename: David J
authors.initials: DJ
authors.lastname: Callans
authors.forename: Edward P
authors.initials: EP
authors.lastname: Gerstenfeld
authors.forename: Erica S
authors.initials: ES
authors.lastname: Zado
authors.forename: Francis E
authors.initials: FE
authors.lastname: Marchlinski
mesh_terms: D000328:Adult; D000368:Aged; D009202:Cardiomyopathies / Q000473:pathology / Q000503:physiopathology*; D017115:Catheter Ablation; D022062:Electrophysiologic Techniques, Cardiac; D056149:Epicardial Mapping; D005260:Female; D006346:Heart Septum / Q000473:pathology / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017180:Tachycardia, Ventricular / Q000188:drug therapy / Q000473:pathology / Q000503:physiopathology* / Q000628:therapy*